Diagnostics on calculations

Species with negative natural orbital occupation numbers

This diagnostic indicates that a
given molecule's electronic ground state
may not be well represented by a single electronic configuration.
See: "A natural orbital diagnostic for multiconfigurational character in correlated wave functions"
M. S. Gordon et al., J. Chem. Phys. 110(9), 4199, 1999
Click on "neg" for model chemistries and occupation eigenvalues.

With larger basis sets (such as aug-cc-pVTZ) many molecules have small negative occupation numbers.
To provide a more useful diagnostic the following list is limited to orbital occupation numbers less than -0.001